How to send picture to the background so i can see the plane?
The fastest way is to add a Background image.  

Add->Image->Background
This will keep your image always in the back.



Even when it's physically in front.


Bonus:
You can change these settings for every image in your viewport.
You can also set your image to only appear in orthographic mode, make it transparent... etc.

Properties panel->Object Data
These settings are available for every image.